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Causes of Alzheimer's

Ken Teegardin Written by Ken Teegardin
SeniorLiving.Org Expert on Chief Editor | Caregiver

Alzheimer’s is an “irreversible, progressive brain disease that slowly destroys memory and thinking skills, and eventually even the ability to carry out the simplest tasks,” according to the National Institute on Aging.

Causes of Alzheimer's

Alzheimer’s infects the senior living community like a plague. It’s estimated that over 5 million Americans have Alzheimer’s. And it’s the sixth leading cause of death in the U.S.

Sadly, there is no cure. In fact, Alzheimer’s disease is still not completely understood. While the effects on the brain are clear, the exact causes are not completely known. Scientists believe that a combination of genetic, lifestyle and environmental factors affect the brain over time.

Before we look at the causes of Alzheimer’s, let’s look at the disease itself.

The Alzheimer’s Disease Process

We still don’t know what starts the disease process. But we do know that damage to the brain can start 10 to 20 years before any symptoms begin.

The brain has 100 billion nerve cells that are interconnected, forming complex communication networks. Groups of cells perform special jobs like thinking and remembering. Alzheimer’s kills some of these cells causing a chain reaction of brain destruction.

It’s believed that two abnormal structures—plaques and tangles—are responsible for killing the brain’s nerve cells.

Plaques are deposits of protein that build up in spaces between nerve cells. Tangles are fibers of a different protein that build up inside cells. Most people develop plaques and tangles as they age. But those with Alzheimer’s develop greater numbers.

Scientists believe that these plaques and tangles block communication among nerve cells until the cells eventually die. This death of cells causes memory failure and personality changes.

Age Increases Risk

While not a cause of Alzheimer’s, age is the greatest risk factor. Most people with Alzheimer’s are 65 or older. Your risk doubles every five years after 65. After age 85, your risk is 50%. It’s still unknown why the risk rises so quickly with age.

Genetic Causes of Alzheimer’s

Two types of genes are factors in Alzheimer’s—risk genes and deterministic genes.

Risk genes increase the chances of developing the disease. But they don’t guarantee you’ll develop it. The APOE-e4 gene is the strongest influence and is seen in 20% to 25% of Alzheimer’s cases. Those who inherit this gene from a parent have a greater risk. Inherit this gene from both parents and your risk goes up more.

Deterministic genes directly cause the genes. If you inherit these genes, you will develop the disease. These genes are amyloid precursor protein (APP), presenilin-1 (PS-1) and presenilin-2 (PS-2).

Alzheimer’s disease with these genes is called autosomal dominant Alzheimer’s disease (ADAD) or “familial Alzheimer’s disease.” People with any of these genes develop symptoms before age 60, some even in their 30s or 40s.

Lifestyle Causes of Alzheimer’s

While not conclusive, evidence suggests your lifestyle may increase your risk for Alzheimer’s. The reason: your brain health is linked to your heart health.

Each heartbeat pumps about 25% of your blood to your head. Your brain cells in turn use 20% of the food and oxygen carried by your blood.

Your risk for developing Alzheimer’s is increased by conditions that damage the heart or blood vessels. Conditions such as:

  • High blood pressure
  • Heart disease
  • Stroke
  • Diabetes
  • High cholesterol

These conditions are brought on by improper diet, smoking, lack of exercise, and excessive alcohol consumption.

Environmental Causes of Alzheimer’s

An early adult head injury is correlated with the development of Alzheimer’s disease. A head injury is one that results in the loss of consciousness for 30 minutes or more. Skull fractures and injuries that result in long periods of amnesia put one at even greater risk.

Other factors thought to increase the risk are lower education levels, non-stimulating, repetitive jobs, infrequent social interactions and not regularly engaging in mental challenges like reading and playing games.


Every year, Alzheimer’s devastates the senior community. And while the science is still unsettled, researchers believe the causes of Alzheimer’s are genetic, lifestyle and environmental. We also know that as we age our risk increases.

Mitigate the risks you can control: lifestyle and environmental. Exercise regularly; eat healthy; wear protective headgear when appropriate; engage in challenging mental activities; make your senior living socially interactive.

For more in-depth information on living healthy, check out "Aging Well: The Choice Is Ours."  You can also find tips on exercising with "Active Senior Living."

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